Adding a layer of rocks, gravel, packing peanuts, other, doesn't reduce or impede drainage, and it doesn't improve it. The soil still retains it's drainage characteristics regardless of whether there is a "drainage layer". If you have a soil that supports 3" of saturated soil (perched water) at the bottom of a container, it will always support that much water - no matter the shape or depth of the container. If you put 3" of gravel or stones - even 12" of "drainage" material under it, the soil will still support the same 3" of perched water. All you will have done: You've reduced the amount of soil in the container and raised the level of perched water so it now sets atop your drainage layer. IF you have a soil that supports a 3" perched water table in a 6" deep pot, and are using a 3" "drainage layer" the soil will be 100% saturated immediately after proper watering. From this, you can see that "drainage layers" are counter-productive unless your only intent is to reduce the total volume of soil in the container (and there are better ways to achieve this) or the soil particles are large enough that they support no perched water, in which case no drainage layer is needed. A 3" layer of saturated soil located several inches above the bottom of the container would be just as detrimental to root health/function as one located at the bottom. Al

Your soil looks like its on the heavy side, I add alot of perlite to my potting mix so that the roots can breath, I think your plant looks pretty healthy, did you just repot it recently? Others will come along and give you great advice, the board is slow on the weekends so hang in there, the photos you posted are great and will be a big help to others.

Let us know if any change. if you think it could be a deficiency the best way is a soil sample to your local extension, and tell them you want to grow raspberries. they will tell you what you need. If you want to just cover all bases. use Holly Tone or any complete balanced organic fertilizer. Dr Earth is also excellent. Many exist. You could add azomite, rock phosphate, also use kelp. This will supply all trace minerals and such. Iron is good too, like Iron-Tone. In the photo I see a small leaf with tip burn. That is usually too much nitrogen. Possible you have a leaf spot of some kind. If not many leaves are like this remove them. You can use copper, sulfur, lime sulfur as a preventative. All organic fungicides. I don't have any fungal problems here, but do use a preventative, as I need it for fruit trees, I hit the brambles while I'm spraying the trees.Usually early in the season before any flowers or berries. I use nothing once flowers form.

Peppers need similar fertilizer to what is used for tomatoes. I use synthetics with a 3- 1 -2 proportion. For example MG 24- 8-18 liquid. I think it has magnesium and sulfur too, which peppers demand. I am sure there are some other brands and types. The one I mentioned is pretty much all-purpose.