Regardless of the NPKs, fish fertilizer is a great organic nutrient that will grow a pepper plant from cradle to grave. But why are you feeding it so often? I've never seen anyone actually overdose a plant with FF. But you may very well be the one to prove that it can be done.
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Too much of any good thing is a bad thing. When you use a nutrient, you can only use up to a certain % of TDS - or Total Dissolved Solids - in your nutrient solution. Once you've exceeded that, you start causing all sorts of problems at the molecular level with the soil. (or in this case, the container media) On the other hand, "fertilizer burn", is dessication of the roots, which makes it impossible for the plant to take up anything at the affected area.
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This doesn't look like a fertilizer burn to me, but it does look like a lockout. Just relax a bit... Don't fertilize those plants for the next 3-4 weeks, and keep an eye on them. During that time, don't expect any growth. Just ride out the situation, and resist the urge to be reactionary. If the situation takes a turn for the worse, you will want to repot them in new media.