I've ferns under high light as well, no problem. Only thing is that the tips being transparent because they grow harder then normal. I use profito as well and think 30 ml is very low dosing for so much light. That is even lower than the recommended dose for your tank, but the light is way more than standard. The recommended dosings from easy life are based on standard dutch/german tanks with low light and few plants. When using more light, they recommend using 2-3 times the dosing.
In my 400L I use 15-20ml daily depending on the plant mass. That brings me to the second point: dosing ones a week is not enough for high light tanks. You should consider dosing daily or bi-daily. Remove most of the old leaves, up the dosing, and wait 3-4 weeks to see what the new leaves look like