A lot of ZLL bulbs and ZHA bulbs are just unreliable repeaters In a smartthings setup except for each other. I’ve seen a lot of different theories as to why, but nothing definitive. It’s just been a fact for four or five years and still seems to be true. The only ones I know that seem to be really solid repeaters for other devices are the IKEA Tradfri. This has often been discussed in the forums, there’s even an FAQ on it, but there really isn’t any resolution except what you tried, which is powering off the bulbs so your other devices will find other parents.
It’s even weirder because this is not true for Zwave: Zwave bulbs seem to be perfectly good repeaters for other Z wave devices. It’s just an issue on Zigbee networks.
So I don’t know what more to say except that it’s a known issue without a known solution. 
FAQ: Are Smart Bulbs Repeaters? (Updated 2019: the new answer is yes, but may be inconsistent)
Tagging @johnconstantelo just in case he has any additional ideas.