Will these NPK 13.13.13 Tablets Hurt my Girls ?

Hello All. I`ve found these Fertilizer Tablets down the local Cheap shop and wondered if they would be ok to use on my 2 Girls ? I`ve been using Tomato Fertilisers that are N4.0 P3 K8.0 and N5.0 P2.0 K5.0 And alternating them every other watering as well as plane water But they are a little Low in the Phosphorus department and i think it`s starting to show a little now ?.
My 2 Girls are 10.5 weeks old and are in B&Q Compost mixed with Crushed Slate (Neutral PH). Growing outside in a Plastic Greenhouse. They have been LSTed and FIMMed about a week ago.
I`m a Professional Plant Killer since birth and nearly killed these 2 with to much Bicarb and Liquid Soap mix for mildew. so please go easy on me as i`m still learning.
Here`s how they look so far...
I have a HUGE Budget of £0.00 to spend so have to make do with what i`ve got so if the Tablets can be used in any way,shape or form ? any suggestions or idea`s would be greatly received
12/12 is on the 25 September here in the UK so i think they will start to Flower soon if thats any help.
Many Thanks for any Help +Rep for Usable Advice

Nice healthy plants, normally go for greater P for flowering period.. npk -15-30-15 or something similar as far as the P is higher !

Trial and error lol. Thats how humans learn and survive. I would give them a try could be the next big thing, ya never know.