First grow greenhouse uk

Think it could be due to heat stress or needs so calmag . have you had alot of sun lately more than usual as we have here. x

Leaves tips yellowing or getting slightly clear white ? Plants looks good, check the EC levels of the drain on next watering, at this stage it should be around 700ppm (1.1ms)

Ok hard to say for sure w/o a picture but in general, so if its outer leaftips on topleafs only it could be lightburn if you had a lot of sun suddenly. But outdoors its very rare unless you had a heatwave in a warm climate. So fishmx can be very potent. You van burn young plants easely, Flush your plants with lukewarm water fast until you have a lot of run- off. Then let your plants dry for at least 3 / 4 days maybe more, until top seems dry again, then slowly start feeding again, very easy on the fishmix, which is very high in nitrogen.

I would say a slight nitrogen deficiency, but at this stage of flowering adding any extra nitrogen fertilizer should be at half strength to avoid burning. Hope this helps, Organoman.

Could be a ph problem. Is the ph in range, if not it may be blocking essential nutrients out.