They both resemble varieties of Metrosideros collina - some of these varieties get to 15 feet or more, but hopefully, you bought smaller varieties, which may only reach about 4 feet. Keeping larger growing shrubs in pots healthy isn't easy because they run out of root room, but yours are not really old enough for that to be the problem.
Looking back at the photos in your Acer question and now these two plants, I would suggest you simply are not watering sufficiently well, especially for plants in sun during the afternoon. I cannot see the size of the pots the Metrosideros are in, but if they are relatively small, they will dry out rapidly.
An adjustment in your watering routine is probably necessary, as follows. Touch the top of the soil in the pot - if it feels dry to the touch, water thoroughly with at least two litres of water, three for larger pots, and repeat the next time the soil feels dry to the touch. That may be every day or even twice a day - you will learn over time how often you need to water. The other thing to consider is, if the soil in the pot has dried out completely, then any water you put in will just run straight out the bottom, without being taken up by the soil. In that case, it's necessary to water well, keeping a tray our outer pot with no holes in it underneath the pot, until all the water that's run through has been absorbed. You may need to do that more than once, if the soil is completely dry. Another way to tell if it's completely dry is to pick the pot up - it will be much lighter than if it's nice and damp, when it will be noticeably heavier.
If there is nothing green left on either plant, they may be dead - you can check by scraping back a bit of the bark or skin low down on the main stems - if they are brownish and dry inside, they're dead, if they look a little moist and slightly greenish, they're not, and new growth should occur IF you water properly.
