Regular MG soil is usually too hot (strong) for seedlings, and could burn (kill) them. Better to start in a seedling mix next time, in a dixie cup, with a little perlite.

Also, not too sure about the manure... Hope you added plenty of perlite.

What size pots are you using?

If the MG doesn't kill your seedlings, then the plants will slowly eat up the nutrients. The nutes will run out in 2-4 weeks, depending on the size of your pot. You should be potting up at least a couple times, so each time you re-pot with fresh soil on the bottom, the plants again receive the nutrients, and do not need to be fed nutrients, just water. Again, after 2-4 weeks, depending on the size of the buckets, plants, rate of growth, etc., the nutes in the MG will run out, and you need to feed with nutes. This is a total guessing game in the beginning, but with a lot of work it can be mastered. This is why growers prefer potting mixes with little to no added nutrients, or hydro for that matter, because you can know what's going better.

Also, the buffers to keep the soil ph balanced will run out after a month or two, and cause the ph to drop suddenly. Could also kill your plants. That's something to watch for down the road.

Like I said about the nutes before, better to get something meant for cannabis like Canna or Foxfarm. With the one you have now, you are probably not getting enough of something, and too much of something else. I couldn't tell what to dilute it at, because it's not meant for cannabis. If you decide to use it, start with very little.