Q.Can My Hoya Plants Be Sprayed All Over With Organic Seaweed Concentrate,
Can my Hoya plants be sprayed onto soil and leaves with Plant Food ORGANIC SEAWEED CONCENTRATE.

Certified GKH Gardening Expert
If it is showing signs of nitrogen deficiency or growing too slowly then it could help! Just keep in mind that if the plant receives too much nitrogen, it may not flower very well or at all.
Here are some articles that will help:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/what-is-foliar-spray.htm
https://www.gardeningknowhow.com/ornamental/vines/hoya-wax-plant/hoya-plant-feeding.htm
https://www.gardeningknowhow.com/ornamental/vines/hoya-wax-plant/growing-hoya-wax-vines.htm