bug attack?

Just recently got rid of a bug problem . Thought it were spidermite st first but then realised after I treated them started seein black flys aka fungus gnats anyways got rid of them and now 6 out of 20 look like this. any ideas why and what this is?

Heres an bit if the info on them ... strain is bubble berry growing in canna pro soil . Nutes are gold label soil a and soil b . Additives are ultra mg by gold label also a drop if superrhrive once a while. That's all Im using at this stage have got mollases and house and garden top shooter to use later on and canna pk/13/14 .

The foliage in its self looks nice healthy and green but 60percent of the plants are deformed

Fungus gnats are very hard to eradicate completely. Are You also sure theres no larvae eating the roots now?