Light green young plant. First time hydro. Probably anxiety.

I'm growing outdoors in a DWC bubble 20litres.
Watering schedule, I guess is constant?
Growing media is rock wool, DWC bucket contents is hard water (about 260ppm out the tap) using air stone.
I planted the seed in soil on the 30th June, moved her to hydro on 17th July.
I'm using Growth Technology Ionic Hydro HW Grow for nutes at 690ppm or 1350μs/cm depending on your preference.
pH ranges from 5.5 to 6.7 during the day but swings up to high 7's (sometimes low 8's) overnight so I pH down with lemon juice or distilled vinegar in the morning when needed.

There was some build-up yesterday that looked like sewage bubbles on the water surface (I'm guessing was the vinegar or lemon juice), so I let 20 litres of water sit overnight, pH'd and EC'd in the morning, emptied and cleaned the DWC bucket and replaced the nute solution.

The pictures are of the same plant within about 4 hours of each other. I got worried 'cause when the sun was out and clear sky, lots of light, my plant looked slightly yellow-green but when the weather became overcast, the plant colouring darkened (obviously because of the sun going behind clouds hurdur) to a more normal colour but now I'm freaking out triggering myself it's something more serious but, honestly, I've not really encountered problems before (in my magnificent number of a previous 3 grows) so this is where experience trumps book/internet reading; I've no idea what I'm looking at.
All in all I'm probably worrying over nothing, and if it is something I'm guessing either a nitrogen def (cotyledons shrivelled and fallen off but afaik that's normal) or something Cal/Mag can fix.

Is there something wrong or am I being a freak about nothing?

In the mean time, let me show off my 5 week flowering 3ft wide Strawberry Eclair just to show I'm not a complete idiot (even though there are some burns because of a strong aphid solution hurrdurrrr)


Edit: cleaned up my syntax and wording
Edit 2: Apology to mods if this post is in the wrong place, wasn't sure if I should post here or in the n00b section. Please move this post if its inappropriate here

She does look light, which would point me toward nitro and calcium. I'm not familiar with your brand of nutes, so can't really advise there (not sure you want my advice as I'm only on my 3rd grow as well)

Johiem said:

She does look light, which would point me toward nitro and calcium. I'm not familiar with your brand of nutes, so can't really advise there (not sure you want my advice as I'm only on my 3rd grow as well)

Click to expand...

Hey man not at all, any advice is good advice, and if you've done 3 hydro grows that's still three more than myself so all is welcome.
Im starting to think it's the hard water nutrients as they compensate the minerals present in my hard water, which could be affecting it. I'll get some CalMag anyway as I know it's useful throughout, if that doesn't work I guess I'm moving to another brand.