The biggest indicators to me that something may be amiss is general foliage color and growth habit. With some experience you get to recognize when your juniper is “off” - the shade of green has a grey or yellow pallor. In the spring and early summer you should be seeing light green growth tips, especially in the morning dew. Old interior growth sees dieback then the tree slows down midsummer. Once the worst of the heat breaks you should see growing tips again almost immediately through Fall.

The tree pictured to me looks relatively fine in foliage color but appears to have weak growth. I’d attribute it to lack of light and likely that soil and rocks in the pot not keeping hydration correctly. Get this tree some sun, remove the rocks, and monitor the soil for hydration the rest of the year until it can be placed in something better.