Bud

you need to understand what you feed your plants to deduce any symptoms. e.g. if you provide lots of calcium, it's not calcium deficiency.. it is lockout. So, do consider recent behaviour. calculate PPMs of what you feed. bloom nutes often have high levels of P and K. If either of these are 'boosted' too high, you will have calcium and magnesium issues... this is predominantly why people think they need cal-mag all the time.. more times than not it is their 'boost' formula or 'bloom' formula... there's no magic bullet. too much is simply too much. good news is that looks mild and isolated. You can take your time with this problem and ensure you choose the right path. also, you are fairly late into the life cycle. Some blemishes are inevitable.. or at least very difficult to avoid 100%. This won't impact quality or yield in any noticeable way, even if it worsens a bit.

Hey friend, Your plant looks everything fine to me.Don’t worry much about these symptoms.You should stick with your blooming nutes and booster.But remember, always adjust your water pH around 6.5 whenever you water.Happy growing... ✌️

Youre only in your fourth week of flower. make sure they are getting enough cal/mag during bloom, and P-K boosters if you want closer to finish, like 4 weeks or so