Pale green/yellow growth after switching to 12/12

Hi All,

I have recently switched my scrog grow from 250w CFL to a 600W air cooled HPS. Since switching, the new growth has been a very pale green, almost yellow colour.

- 600w HPS.
- Deep water culture.
- 8days into 12/12.
- Vitalink nuitrients.


I know its not the heat as my cool tube is cool enough to touch (canopy 8-10"s away ). However, I am starting to think that it could be either: 1. Light bleaching 2. N def or 3. Nute lock (Vitalink is very strong stuff) . I usually continue with the 'grow' nutes 10-14 days after switching to 12/12, But due to an accidental spillage I have only got part B of the grow nutes left. To make matters worse, my local hydro store has been closed

I have been rummaging through my garden shed and have found some seaweed extract (should be very high in N) and some liquid miracle grow. My question is:

Can I use the grow A with bloom B to increase N in res?

Can I use the MG or Seaweed gel as a subsitute until I can order some Vitalink?

Does this sound like nute lock or too much light?

Apart from the pale new growth everything else seems okay

Thanks in advance

Edit: Current nutes in res is vitalink bloom a+b.

without pics it sounds like normal growth with maybe a little n def. new growth will be a little lighter in color. what is ph and res temp?

Res temp: 74F or 23C
Res PH: 5.9
Res size: 50litres (1 plant)

I will try and get some pictures on here as soon as I can.

Thanks for the prompt reply dude.

Also, at the moment the res contains Vitalink bloom and supervit (didn't make that very clear in OP)

res temps will get you if you dont try to keep them below 70f. for veg and first two weeks of flower i like to keep the ph at 5.4-5.6, this lets the plants get more of the elements it needs for growth. then 5.7-5.9 for weeks 3-5, and 5.9-6.1 for finish.

Cheers dude (+rep) I have lowered ph to 5.5 and removed heating element.

When do you usually start with the bloom nutes?

i do half bloom, half grow for first two weeks of flower.

monitor it and get a nitrogen additive if the new growth doesn't darken up

Cheers guys.. I don't think it's enough of an emergency for me to be adding any miracle grow. I am going to order some more grow nutes (will need them for the next batch anyway). I have also been doing some reading and decided to add a few tablespoons of epsom salts into the res incase its a sulfur def.

Thanks again for the replies

So I managed to get a few pictures. Just wondering if some of the experienced guys can have a little look at these

Res temps: <70F
Ph: 5.5-5.7
Air temp (day): ~82F
Air temp (night): ~73F
EC/PPM: 1.4 / 979ppm

I know new growth tends to look more pale, especially considering that I have recently switched from a CFL to HPS. However, do you guys think they look short of sulfur or nitrogen?

looks like nitrogen to me, the whole plant could use a little darkening.

it's the change in light!!!

the new, harsher light's are speeding up photosynthesis, changing the chemical composition of the plant (chlorophyll).

Don't add further nutes, you will cause problems unless you add a specific nitrogen compound.

i go from t5's to 2000w hps and color stays nice. could be a combination.

Firstly thanks again guys

I don't usually have this problem - that's why I was a little worried.

My plan is too do a res change tomorrow (as normal) using a mix of bloom and the last of the part B grow nutes that I have.

e.g
100ml of A bloom
70ml of B bloom
30ml of B grow.

Not entirely sure you can do that, but it will tide me over until my new nutes arrive during the week.

Holla if that's a dumb idea lol if not cheers for your help