Too close isn't always good. Bees don't forage heavily within so many feet of their hives. I don't remember the distance but I'm sure you can Google it. Now early in the season when there isn't much blooming they wrap up any Holly bush in my mothers yard. Those are all 100 or more yards from the hives. The same may be the case with your Tallow trees. There may not be much else blooming.

They will occasionally forage pretty close but IIRC it's something about their "waggle dance" that doesn't work close up.

I am now back up to 16 hives, counting nucs that I have, and I have seen about 5 bees on plants around the house all day.

There's way over 500,000 bees within 1/4 mile of my house and I rarely see one unless I'm standing at the hives. Now a "neighbor" about 3/4 mile from here has them in her yard all the time.

I am definitely not an expert on Tallow flow since we don't have any/many here, but I have read a good bit about it. Supposedly it's a very heavy flow and hives can run out of room quickly. If you don't have a super on your hive yet, I'd get one on there and check it every 5-6 days and see if they need another.

If my people, who are called by my name, will humble themselves and pray and seek my face and turn from their wicked ways, then will I hear from heaven and will forgive their sin and will heal their land. 2 Chronicles 7:14